1. Field of the Invention
This invention relates to a commercially feasible process and apparatus for neutralizing nitric acid with ammonia whereby the "smog" formation usually associated with such neutralization is effectively avoided. More particularly, the present invention is concerned with an apparatus configuration which substantially reduces the amount of ammonia, nitric acid and/or ammonium nitrate evolved into the atmosphere during the production of ammonium nitrate from nitric acid and ammonia.
2. Description of the Prior Art
In Applicants' prior application Ser. No. 152,063 filed June 11, 1971, now U.S. Pat. No. 3,758,277 and Ser. No. 260,392 filed May 18, 1972, now U.S. Pat. No. 3,870,782, Applicants disclosed an ammonium nitrate neutralizer which would significantly reduce the degree of "smog" formation which previously occurred during ammonia-nitric acid neutralization procedures. Those earlier studies resulted in development of apparatus and methods which succeeded in reducing ammonium nitrate emissions from what were previously considered to be good emission control levels, i.e. three to five pounds per ton of recovered product ammonium nitrate down to 0.78 pounds of ammonium nitrate and 0.77 pounds of ammonia per ton of product ammonium nitrate. These reductions in emission levels represented a substantial improvement over the emission levels previously being suffered by prior art processes.
Anticipated changes in Government standards with respect to ammonia emissions, however, are expected to require even better results for control of ammonia emissions. Applicants at first considered that their previous apparatus could meet such increased standards. It was considered that, by varying the acidity within the first and second reaction zones, the degree of ammonia emissions could be reduced. However, when the acid content was varied, it was found that either the rate of ammonia emission was not reduced, or it was found that the rate of nitric acid or ammonium nitrate emission rose significantly.
In the prior apparatus, a deflector was situated above the outlet of the second reaction zone, which was situated within the core of the apparatus. The core of the apparatus defined a first reaction zone, which was situated outside the core of the reactor, and thus outside the said second reaction zone. The vapors and liquids fountaining from the second reaction zone hit the deflector and the liquids were deflected downwardly into the second reaction zone. The vapors would pass around the deflector and would pass upwardly toward the gas outlet. In arriving at the present invention, it was first considered to situate the deflector such that both the liquids and the vapors fountaining from the second reaction zone were deflected entirely into the first reaction zone. It was theorized that any ammonia gases emitting from the second reaction zone would be brought into contact with the acid conditions in the first reaction zone and hence the scrubbing action in the first reaction zone would scrub out any ammonia. It was found, however, that when this was tried, the level of ammonia nitrate and nitric acid emissions rose drastically to levels comparable to previous prior art equipment.
A need, therefore, continued to exist for a method and apparatus of further reducing the levels of particulate ammonium nitrate, ammonia and/or nitric acid evolved during the production of ammonium nitrate.